Fire extinguishing composition comprising a fluoroaliphatic surfactant fluorine-free surfactant

ABSTRACT

Compositions are disclosed which form tough, durable, rapidlyforming and spreading films on the surface of hydrocarbon liquids comprising in combination a water-soluble fluoroaliphatic surfactant and a water-soluble synthetic imputrescible hydrocarbon-congruous organic fluorine-free surfactant and water. The films formed by these compositions are especially effective in suppressing the vaporization of hydrocarbon liquids into the air and are, therefore, useful for extinguishing liquid hydrocarbon fires.

lUite Sttes Patent [191 Francen 1*Nov. 13, 1973 FIRE lEXTllNGUlSHING COMPOSITION (IOMPRISING A FLUOROALKPHATIC SURFACTANT FLUORlNE-FREE SURFACTANT Inventor: Vernon L. Francen, Roseville, Minn.

Assignee: Minnesota Mining and Manufacturing Company, St. Paul, Minn.

The portion of the term of this patent subsequent to Feb. 19, 1988, has been disclaimed.

Filed: Feb. 5, 1971 Appl. No.: 113,022

Related US. Application Data Continuation-impart of Ser. No. 840,102, June 12, 1969, Pat. No. 3,562,156.

Notice:

US. Cl 252/8.05, 252/2, 169/1, 252/3, 252/307, 252/354, 252/355, 252/356, 254/357 lnt. Cl A62c l/12, A62d 1/00 Field of Search 252/23, 6.5, 8.05,

[56] References Cited UNITED STATES PATENTS 3,562,156 2/1971 Francen 252/805 3,258,423 6/1966 Tuve et a1 252/8.05 X 3,475,333 11/1967 Meldrum et a1. 252/3 3,047,619 7/1962 Brace t 260/500 3,476,819 11/1969 Trischler 260/653 Primary ExaminerGeorge F. Lesmes Assistant Examiner-M. B. Wittenberg Attorney-Alexander, Sell, Steldt & Delahunt [57] ABSTRACT 6 Claims, 2 Drawing; Figures FIRE EXTINGUISHING COMPOSITION COMPRISING A FLUOROALIPHATIC SURFACTANT FLUORINE-FREE SURFACTANT This application is a continuation-in-part of my application Ser. No. 840,102, filed June 12, 1969, now U.S. Pat. No. 3,562,156. vaporization The present invention relates generally to compositions for the preparation of tough, durable, rapidlyforming and spreading films on hydrocarbon liquids comprising in combination a water-soluble fluoroaliphatic surfactant, a water-soluble synthetic imputrescible hydrocarbon-congruous organic fluorine-free surfactant and water with or without a stabilizer. These films can be formed and spread over the surface of a volatile water insoluble liquid to provide an effective barrier to vaporization of the volatile liquid into an adjacent volume of air.

At the present time, substantially more than 1-% billion metric tons of petroleum products are produced annually. These materials find their way throughout the world in tanks, ships, trucks, railroad cars and pipelines to storage tanks, processing plants, and untimately, to the consumer in drums, tanks, cans and bottles. Most of these petroleum products have a significant vapor pressure under the conditions of use and storage, and are thus continually evaporating into the air at each point of transfer, shipment and use. There are a number of obvious disadvantages to this free evaporation of volatile hydrocarbon materials. The simple economic loss may be significant; for example, in the handling of gasoline, the loss through evaporation between the refinery and the automobile can be as great as 5 percent of the product. Of greater significance, perhaps, is the situation in an area such as Southern California where the presence of large quantities of hydrocarbon materials in the air has been cited as a major factor in the smog problem. The evaporation losses occasioned in the processing and handling of petroleum products approaches the hydrocarbon output (combustion byproducts) produced by automobiles. The most spectacular and pressing problem of free evaporation of hydrocarbon materials is the fire hazard involved. These materials are generally highly flammable and their vapors can form combustible mixtures with air. Adventitious sparks or other sources of ignition can result in a disastrous fire especially in the case of pipelines or large scale storage facilities. The threat of a major fire in a refinery tank farm, a service station, or on the decks or below deck areas of an aircraft carrier is an ever present hazard. Spills, whether resulting from an accidentally open valve, an overturned or broken container or an overturned tank truck, represent an immediate potential hazard. A positive, readily available, simply applied method for stopping the evaporation of flammable liquids under these conditions would represent a marked and significant improvement over present procedures.

It is accordingly an object of the present invention to provide compositions which can be used to form tough, durable, rapidly-forming and spreading vapor barrier films on hydrocarbon liquids.

Another object of the invention is to provide concentrate compositions which form water-containing surface films which inhibit the release of flammable vapors from a hydrocarbon liquid surface.

Other objects and advantages of the invention will become more fully apparent from the following detailed description.

The ability of surface films to minimize evaporation has long been known. Typically, a film, for example of cetyl alcohol, can be spread upon a reservoir in desert areas and cut the evaporation of water to one-half the evaporation level of water in the absence of the film. In a 1962 publication (Guenthner and Vietor, Industrial and Engineering Chemistry, September, 1962, page 168) it was recognized that fluorochemical compounds could be utilized to form barrier films for evaporation suppression on gasoline. The authors state that the addition of 0.003 percent fluorochemical can reduce the evaporation of the gasoline under static conditions to the point of nonflammability. The restriction to static conditons points out a very significant limitation to the effective use of such films. In order to be an effective evaporation suppressant, it is necessary that the barrier film be rapidly formed initially and again after disturbance, and that the film be sufficiently mobile and capable of remianing remaining under conditons of motion so that it will establish and maintain a substantially continuous barrier. The fluorochemical film-forming systems known up until now have, however, formed films relatively slowly and have been incapable of maintaining or rapidly reestablishirig a satisfactory barrier film after disruption by agitation.

A recent development related to the extinguishing of burning fuel, Tuve and .lablonski U.S. Pat. No. 3,258,423, is directed to films comprising water and specific fluorochemicals to produce a film on the fuel surface which cuts down the rate of evaporation so that reignition becomes difficult or impossible. This invention has resulted in the development of a fire extinguishing system vastly more efficient than any preceding methods. However, only a relatively few fluorochemicals in relatively high concentrations can be used to form such aqueous films resulting in an undesirably high cost for the fire-fighting composition.

The compositions of the present invention form tough, mobile, rapidly spreading, readily healing vapor barrier films. They can be formulated with lower quantities of the more expensive fluorochemical component than was necessary to achieve equivalent results with prior systems. They can be stored as dilute aqueous solutions in readiness for use particularly for preventive applications, e.g., prevention of fires from spilled fuels. More commonly, they will be distributed and stored as a concentrate which can be diluted at the time of use. A particularly desirable commercial item is a material which, at the time of use, would be diluted in the ratio of six volumes of concentrate to 94 volumes of water, i.e., diluted with about sixteen parts by volume of water. Standard commercially available mixing and dispensing equipment, e.g., fire-fighting equipment, is commonly available for this particualr concentrate.

Many of the compositions, in addition to forming a vapor barrier film, will, when mixed with large quantities of vaporized propellant or air, form relatively stable foams, particularly for the extinguishing of large fires. In some cases, it may be desirable to add an auxiliary foaming agent, such asa partially hydrolyzed protein, and/or auxiliary agents such as foam stabilizers exemplified by high molecular weight polyoxyethylene glycol (e.g., Polyox) and an alkyl ether of an alkylene glycol (e.g., butoxy hydroxy-ethoxy ethane) or freeze resistant components (glycerol or ethylene glycol). Generally speaking, these compositions are compatible with solid fire extinguishing agents such as powdered potassium bicarbonate.

The following tests and test procedures have been devised as convenient laboratory guides for determination of the performance characteristics of the various compositions. It has been found that compositions which passed these laboratory tests generally performed adequately in large scale field tests. Perhaps of more significance is the fact that compositions which failed the laboratory tests did not perform acceptably in field tests. I

It should be recognized that the test hydrocarbon fuel used herein, cyclohexane, is a relatively difficult substrate on which to form films. In general, aromatic hydrocarbons such as toluene or xylene or higherboiling aliphatic hydrocarbons such as gasoline, kerosene and fuel oil permit the formation of films at lower concentrations of surfactant. Accordingly, films formed on cyclohexane can be expected to be more effective films on the latter classes of hydrocarbons at any given surfactant concentration.

FILM FORMATION AND SPREADING TEST 1. Five drops of the test solution are placed in the center of a clean surface of cyclohexane contained in a 145 mm. petri dish at about 25 C.

2. By using reflected light, the time in seconds required for the applied solution to spread across the cyclohexane surface to the dish is measured (film speed).

SEAL TEST 1. Following Step 2 above, 15 additional drops of test solution are placed on the cyclohexane surface distributed equally over the surface.

2. 60 seconds after the first of the additional 15 drops of test solution is added, a flame probe is passed (but not touching) over the cyclohexane surface. This result is an indication of vapor sealing. About 5 seconds should elapse before vapor burning is observed.

BURNBACK RESISTANCE TEST RESISTANCE TO AGITATION 1. This test consists of using the result of Step 1 of the seal test. A glass rod is used to agitate the fuel surface while a flame is held over the area of agitation (but not touching the fuel surface).

2. The time to ignition of the fuel is noted;

The compositions of this invention comprise in combination a fluoroaliphatic surfactant, a water-soluble synthetic imputrescible hydrocarbon-congruous organic fluorine-free surfactant and water. The fluoroaliphatic surfactant is a composition including in the same molecule both a fluoroaliphatic radical and a water solubilizing group, generally represented as (R,),,Q,,,Z. The particular structure of the fluoroaliphatic surfactant is not critical; rather it is the balance of the physical properties of the compound that determines its usefulness for the purpose. It is necessary that the combination of fluoroaliphatic radical and water solubilizing group be so balanced as to provide a solubility in water at 25 C. of at least 0.01 percent by weight. It is preferred, particularly in the case where a concentrate is prepared, that the solubility in water be at least about 0.15 percent by weight. In order to function effectively as a film-spreading agent, the surfactant must be sufficiently surface active to provide a surface tension of less than about 28 dynes/cm., preferably less than 23 dynes/cm., in aqueous solution at a concentration of about 0.25 percent or less.

If the fluoroaliphatic surfactant is too soluble in hydrocarbon liquid, it will be extracted too rapidly from the aqueous film to provide sufficiently durable coverage. In general, this requires the presence of at least about 20 percent by weight of fluorine, i.e., carbon bonded fluorine, in the surfactant.

To possess these properties, the fluorinated aliphatic radicaI GR where n is 1 or 2, can be generally described as a fluorinated saturated monovalent nonaroiiiatic radicalof at least? carbon atoms. The aliphatic chain may be straight, branched, or, if sufficiently large, cyclic and may include oxygen or trivalent nitrogen atoms bonded only to carbon atoms. A fully fluorinated radical is preferred,but hydrogen or chlorine atoms may be present as substituents provided that not more than one atom of either is present for every two carbon atoms, and preferably, the radical contains at least a terminal perfluoromethyl group.

While radicals containing a larger number of carbon atoms will function adequately, compounds containing not more than about 20 carbon atoms are preferred since larger radicals-usually represent a less efficient utilization of fluorine than is possible with shorter chains. Fluoroaliphatic radicals containing about 5 to 12 carbon atoms are most preferred.

The water solubilizing polar group Z represents an anionic, acationic, a non-ionic or ampholytic moiety or combination thereof. Typical anionic groups would include CO H, CO M, SO H, $0 M, SO I-I, $0 M, OP- (OI-I) and OP(OM) where M is a metallic ion, such as sodium, potassium, calcium, etc. Typical cationic groups would include NH NI-IR, where R is a lower alkyl group such as methyl, ethyl or butyl, NR A, where R is a lower alkyl group or hydrogen and A is an anion, such as chloride, sulphate, phosphate, hydroxyh etc 'lypical non-ionic groups would include NR 0 and those derived front polyethylene oxide and mixed polyethylene oxide-polypropylene oxide polyols. Typical mixed or ampholytic groups would include N(C H OH NHC H NHC H,NH,, N(CH3)2C2H4CO2, H)2 0, the like.

The linking group Qm, where m is an integer from 0 to 2, represents a multivalent, generally divalent, linking group such as alkylene, arylene, sulfonamido alkylene, carbonamido alkylene and the like. It will be noted that in some instances more than one R, group may attach to a single Q group and in other instances, a single R, group may be linked to more than one Q group, or may be linked by a single Q group to more than one polar solubilizing group. A

With certain fluorochemical surfactants, simple aqueous solutions thereof have been found to spread and form films on a hydrocarbon fuel surface. In genera], however, such an aqueous fluorochemical surfactant solution, although the surface tension is below 28 or even below 20 dynes per centimeter, spreads slowly and does not provide a satisfactory film. By utilising the fluorochemical surfactant also are shown to produce films comparing favorably with the film formed by the aqueous fluorochemical surfactant solution at much higher concentrations.

teachings of the Pf y Such Table 2 presents further data confirming the results fofmlng fluofochemlcalwatef Solutions can be Caused reported in Table l and illustrates the general nature to provide a stable film, the inherent film-forming tenofthgppesent tfiscovery, yin that any film-forming dency of the fluorochemical surfactant being enhanced fluorochemical surfactant water solution can be caused by the addition of a compatible water-soluble fluorineto provide a more durable and stable film in the presfree surfactant. Compatability here means that the two ence of a compatible fluorine-free surfactant. types of surfactants, fluorine-containing and fluorinelil fgliqwp tgl l T bl in -g l d gi free, do not interact to produce an inactive product. fashion the active role assumed by the fluorine-free sur- This is, a non-ionic fluoroaliphatic surfactant can be factant in the film-forming function of aqueous mixed with a non-ionic, an ionic, or a cationic fluorinefluoroaliphatic surfactant solutions. The particular free Surfactant; Similarly, a non-ionic fluorine-free surl5 fluoroaliphatic surfactant having the structural formula factant is compatible with all three classes of the shown did not form a surface film at any concentration, fluoroaliphatic surfactants. However, acationic surfacbut with the addition of certain fluorine-free surfactant is not compatible with an anionic surfactant and tants, films were formed as shown in the Table. The forsuch combinations must, in general, be avoided if satismulation used for this Table was as follows: factory film-forming characteristics are to be realized.

The following Tables graphically illustrate the reinweight forcing role of the fluorine-free surfactant in the filmm H forming characteristics of aqueous fluoroaliphatic surg u u z gfl s g z -h i lz 8-32 uorineree su actant factant solutions on a hydrocarbon fuel surface, in this polyoxyethylenc glycol (PQIYQX N40) 054 case cyclohexane. Water Remainder TABLE 1 FC Fluorine- FF Film properties 50% conc., free cone, burnweight surfactant weight Speed Seal back Fluorochemical surfactant (FC) percent (FF) percent Film (sec.) (sec.) (sec.)

0 36 Yes... 12 +15 3 Yes-.. +15 3 a- O l. ciFISCONHCQHBNWHQWQ--- 0.023-..-110 3:33 fiijjjiif i ifli 3 3 0.023 Plglgiiic 0.25 Yes .do 15 3 0023 Aerosol OT- 0. 25 Yes.-. 7 +15 10 TABLE 2 Film properties 50% F0 conc, Fluorine-free FF conc, burnweight surfactant weight Speed Seal back Fluorochemicel surfactant (FC) percent (FF) percent Film (sec.) (sec.) (sea) -1 1 "1 .5; "65.. gay slight-... IS Ilot covered... +12 10 0. uronic 6 es.- ow 0 C7FHCONHCSHBN+(CZH5) II Q36 Tetronic 25 25 5 0. as Ammonyx L0. 0. 25 25 3 0.36 0 0 0. 36 Pluronic P-94- 0. 3 0 [C7F15CONHC3H N (CH3)a]zSOF .a O. 36 Tetronlc 904- 0. 25 15 0.36 Tergitol 7. 0. 3 3 0.36 Ammonyx L0. 0. +15 9 11 0.36 0 u CuFnSOzN (C1115) C2H OP(0H)z 0.36 PllllOIllO P-94. U U or CONHCHN(CH) CHCOOi 1 dj b t 37 Rmxal 0 0 1 3 3 2 2 4 v 0. Tetronic 904... +15 15 7FitC H N(C a)2CsHeN C2 ACOO (136 Ammonyx +15 25 NoTE.-Tetr0nic 9041s an ethylene thiamine-propylene oxide-ethylene oxide adduct having the structural formula:

H(C2 4 )y(C3H6Ok (C8H5O) (C2H40)yH NCHzCHgN H(CzH40) (C:Ha0)X (CaHoO),(C2H40) H w with an ethylene oxide content of 40 percent and a molecular weight of 7,500.

t m fiet aee i .twi l w that hpaeh t e TABLE 3 fluorochemical surfactant is capable of forming a fair Emulsilfi- Film properties 52% 11 nfilm at relatively h gh concentrations, a superior film is i Speed Seal back formed at a concentration level where no film was Fluorine-free Surfactant (590-) Film (56) (5%) (5%) formed by the aqueous fluorochemical surfactant solu- Pluronic L-62 20 %es. +3 3 tion by the addition of an anionic fluorine-free surfac- 212 ;221:131: 15 31 2:: g fig g i Pluronic es... tant, viz., Aerosol OT. The addition of other fluorine Triton X400 n 15 Yes 21 +30 2 free surfactants at the no-film concentration of the aw y-12s. 15 Yes... 16 25 2 mm a M .1. 8 was and n6 oU 2o Hz 2 H m: o 072 920 m mm o i i OTRQH u n Z B avo w M w mwmmfioidoid was 92m om oo we w h m 8d ---m5oifiwzfi oemovm oo e o and oofi ox movz wdomzoo m on m Em a Z. 5. mg -m ooqeomzfi oz qmovmo o we u mfi fiw wj i mfifififi fifik5-..-... .HHH ,HHHHfiwwfifim s m mmc N mg 3 5 0ofi omztm ozfimovm oc m o E kn wwwm i an e ooEGxEQz m omzoo fio 8a m i 1 r r r r t 1 l I I I r 1 I v r I mod I- q a a a a N 2 w wuawowwz mmwwwww ww w w HHH and J2 2558. mm HHHHHHHHHMHHHMHHuwflmmwmwmmm fi wm wfi mfi g m E...-..--.-.-.-..--.---H.HHU E% E- y mmwn n w s... M i r i w u 2 a M mm w .E .c.$e .wew m.e .....Pe.@..7...o.m..-.o= M2. V 2.22m and M -imor 3 m oem ovz o W56 o m 633 Q88 fioomv 2595a .5 saw 2...... 5.2; fia .22.... 2 mg 2.5.5. 2. 6: m oaoa 85H 00 26D 98 a named. 0 0 5 5 l 2 2 w .5 w m 6 TABLE 3 nnlinucd 0- M Ma b s l) e a. i ec m s... D m D. mM 8 F n nne) m wmc ltie um l m E t n a t c .m r u S 8 e 4 e n n o u 1 F 5 Yes-.. Yes... 15 Yes... 10 Yes... 200 Yes-..

Sulfa betain 1) Triton X-67.

l Pluronlc P-94 at 0.16%.

As earlier noted, compositons according to the present invention were formulated with and without a stabilizer component. The following Table 4 graphically demonstrates the reinforcing effect of the stabilizer component in the characteristics of the formed films.

The formulation for the compositions reported in this Table 4 included the components in the stated quantities, the remainder being water.

The film-promoting fluorine-free surfactant must be water-soluble in order to be satisfactorily applied, although, of course an insoluble excess over a truly soluble amount can be dispersed within an aqueous carrier to be subsequently dissolved, for example, on dilution of a concentrate to the final film-forming solution. For convenience, however, the fluorine-free surfactant in no improvement in the spreading characteristics of the film-forming fluorochemical surfactant-fluorinefree surfactant aqueous solution, i.e., the fluorine-free surfactant must be hydrocarbon-congruous. On the other hand, if the fluorine-free surfactant is too soluble in the hydrocarbon fuel phase relative to the water phase, it will be rapidly removed and the film will collapse too rapidly to be useful. Suitable fluorine-free surfactants are characterized not so much by the absolute solubility of the material in the hydrocarbon fuel phase, as by the distribution of the material between the hydrocarbon fuel phase and the aqueous phase. As

used herein, the term fluorine-free refers to a compound which is free of fluoroaliphatic radicals and contains no more than at most, five percent carbon-bonded fluorine by weight.

In addition to being water-soluble and hydrocarboncongruous, as earlier noted, the organic fluorine-free film-promoting surfactant of the present invention is also synthetic and imputrescible. Since the compositions of the present invention are intended to be stored,

either in concentrate form or as dilute aqueous solutions, for extended periods under varying environmental conditions it is highly desirable that the fluorine-free surfactant component be non-putrifying to insure storage stability of the composition and, secondarily, provide for odor-free compositions in use. It has been found that certain synthetic organic compounds possess these qualities in addition to other qualities hereinbefore and hereafter set forth.

One method for selecting suitable fluorine-free surfactants is the determination of the efficiency of the surfactants in promoting aqueous emulsions of hydrocarbons in water. The test can be carried out very simply by adding to a standard container equal volumes of a test hydrocarbon, such as cyclohexane, and water to gether with a small amount of the fluorine-free surfactant to be tested. Agitation is started at a standard rate and the time determined at which the two-phase system acquires the high turbidity characteristics of an oil-inwater dispersion. Since the change from the coarse mixture to the uniform dispersion takes place over a very short period of time, this test develops into a very precise measurement. In general, fluorine-free surfactants which, under the below noted standard test conditions, provide an emulsion in 200 seconds or less also act to promote formation and spreading of films of fiuoroaliphatic surfactantwater solutions on hydrocarbon substrates.

The test is carried out in a 100 ml. beaker, cm. in diameter X 6.5 cm. in height, equipped with a conventional magnetic stirrer bar 2.5 cm. in length and 0.95 cm. in average diameter. The stirrer used is obtainable from the Chicago Apparatus Co. under the tradename Magnastir." For each of the tests, ml. each of distilled water and cyclohexane were used together with 0.25 percent by weight of the particular fluorine-free surfactant to be tested according to the following procedure:

l. The water phase consists of distilled water containing 0.25 percent by weight of the fluorine-free surfactant to be tested.

" 2. The water phase is placed in he ssker'rsiiswa by the careful addition of the cyclohexane phase.

3. The stirrer bar is introduced and rotated at a speed of l250i250 rpm.

4. By using a light focused into the solution, the time in which an emulsion is formed is tested this is indicated by a change in color from clear to white.

Table 5 Fluorine-Free Surfactant Emulsion time Seconds 1 13. Ammonium alkyl phenoxy polyoxyethylene sulfate (Alipal CO 436', General Aniline and Film Corp.) M. Amphoteric fatty acid amido complex (Antaron FC; General Aniline and Film Corp.) 25

15. Phosphate ester of a higher fatty alcohol mixture (Gafac RS 710; General Aniline and Film Corp.) 15 C H CO,N(CH,CH,0H), 30 17. Alkoxy polyoxyethylene oxyethanol (Triton X 67 Rohm and Haas Co.) 200+ Octylphenoxy polyoxyethylene oxyethanol (Triton X 100 Rohm and Haas Co.) l5

l9. Nonyl phenoxy polyoxyethylencoxy ethanol (Triton N 128 Rohm and Haas Co.)

20. Sulfonated aliphatic hydrocarbon oil (Calsolene Oil RS: Imperial Chemical Industries 2]. Polyoxyethylene Esters of Mixed aliphatic carboxylic acids Oil Soluble Hydrocarbon sulfonates (Witco 912; Witco Chemical Co.)

22. Tetronic 904 Another convenient method for selecting suitable fluorine-free surfactants is determined by the Film Formation and Spreading Test, above described. Those fluorine-free surfactants which, when added to nonfilm-forming fluorocarbon surfactant solutions cause the resulting solutions to form films which spread over the surface of the cyclohexane in 60 seconds or less have been found to be satisfactory film-forming promoters.

A third and generally more convenient test for selecting suitable fluorine-free surfactants has recently been developed. Surfactants passing this modified emulsion test are found to form vapor-suppressing films on the surface of cyclohexane, generally within a time of about sixty seconds or less.

The present modified emulsion test consists of placing, in a 23 X mm vial, 10 ml of cyclohexane and 10 ml of a 1 percent (or 10 percent) by weight aqueous solution of the test fluorine-free surfactant. The vial is then shaken vigorously for 25 complete cycles, allowed to settle for 30-60 minutes, and the contents examined.

Three resulting situations are recognized:

11. Two clear phases, a cyclohexane upper layer and a lower water layer.

2. Three phases consisting of an upper cyclohexane layer, a lower water layer, and an intermediate layer which is an emulsion.

3. Either a) a single emulsion phase or b) a combination of one clear phase, either cyclohexane or water, and an emulsion phase.

When this step of the emulsion test fails to produce at least one completely emulsified phase with a l percent surfactant solution, the concentration is increased to l0 percent, the test repeated, and the results observed.

In the first two situations, where both a clear aqueous and a clear cyclohexane phase are found, the test surfactant is not useful and will generally fail to provide a suitable film on cyclohexane.

Where at either concentration at. least one of the phases has become substantially completely emulsified, the test surfactant is useful and will generally, in combination with a compatible fluoroaliphatic surfactant, under laboratory or field conditons, provide a vaporsuppressing aqueous film on a volatile hydrocarbon surface.

The film formation test was carried out in a mm Petri dish containing a thin layer of cyclohexane. Test surfactants were dissolved in water also containing 0.5 percent by weight of a compatible fluoroaliphatic surfactant and 3 percent of butoxy hydroxy-ethoxy ethane (ButylCarbitol As indicated in Table 6, which represents a cross-section of materials tested, the concentration of test surfactants varied, some being adequately effective at lower concentrations than others.

Five drops of the aqueous solution were placed at the approximate center of the cyclohexane surface and the spreading of the film observed. No particular effort was made to find the optimum fluoroaliphatic surfactant or to determine the minimum effective concentration, since the data serve primarily to establish the correlation between emulsifying surfactants and filmformation.

In the Table, the test surfactants are grouped according to class, and generally from smaller to larger molecular weight in a series. The first column shows the composition of the surfactant, according to the best available information. (Since these are commercial materials, the composition given may be that of the major component or represent an average of a number of Thus, examination of Tables 3 and 6 will reveal that the fluorine-free surfactants which promoted the formation of useful vapor suppressing films had (1) emulsification times of 200 seconds or less, or (2) resulted components.) The second column identified the matein solutions which formed films which spread over the rial by trade name where applicable. The third and fouy l h Surface i 60 Seconds or l o (3) rth columns indicate the emulsification test results at, f d ith a i l i phase or b a r p y, 1 Percent Percent Concentfflbination of one clear phase (cyclohexane in water) and tion of the fluorine-free surfactant. A indicates esan l i h s sentially complete emulsification Of at least one Of the 10 characteristically addition of a water oluble elecinitial phases. trolyte such as sodium chloride, magnesium sulphate The fifth Column designates the compfitlble and the like, to an aqueous surfactant solution tends to Phatlc Surfactant used In the film formmg evaluatwn, decrease the solubility of surfactants and not infreabbreviated as fO l sI quently causes the surfactants to precipitate. Surpris- 5 ingly it has been found that the presence of an electro- P- F ONCHCHOPOOl-l 2 2 5) 2 )2 lyte dissolved in the water (even at concentrations as n |1 2 a 0 3)3 80 P high as 7 percent by weight or more) does not decrease CRpl1SO2NHCaHflN(CHa)aC1 percent the efficiency of these fluorine-free surfactantfluoroaliphatic surfactant solutions. In many cases, it S CBFi1SO2N C2H5)czHosoaNa 20 actually improves the film-spreading characteristics. The sixth column indicates the concentation of fluo- Not only does this simplify the requirements for diluent rine-free surfactant in the aqueous solution. water in making up film-forming solutions for applica- The final column indicates the results of the film test. tions to fu l surfaces, but it ll ws th use f these Satisfactory surfactants form films that cover the entire i d f t t l ti f l on hi at sea Surface in ab ut 6 Seconds 0r less, a are designated where the only convenient diluent water available is sea failure to form a film at reasonable concentrations water with its relatively high salt content. or formation of a film at an undesirably slow rate, is in- I certain li ti i ll he corrosion f dicated by the fire-fighting apparatus may be a factor, it would be TABLE 6 Emulsiflcation Film percent Structure Name 1% 10% FC HO Cover C1H15CO9NB. 0. 1-2 CraHz'lCO 8 0.5 C17H3JCON(CH3)CH2CO2 a-- SarcosylO. 0.15 C11H CON(CH3)CHzCOzN8.. Sarcosyl 0.1 C HuSO Na Alkan0l189S.. 0.25 cmctHisoaK Stepanate K- 0. 1-2 C 2H25COH1OCaHa(SO3N8):.. Benax 2A1..." 0.25 C HnOBOaNa Sipex O 2.0 CnHuOSOaNH. Sipon WI)" 0. 25 C aI-Ia1N(CHgCH2C02N8)2 Deriphat154 0.15 CHH25N(CII3)2(CH2)2SO3... Sulfobetaino 0. 25 CBIIHOQCCIIiCII(COICBIIIT)soaNa Aerosol OT.. 0. 25 CnHnCON(CHa)CzH4S0 Na 1 0.50 CnHmKOCzHONOSOzNH S 0. 25 0. 25 0.1

For pluronic structures see Table 8. Pluronic F 68. Pluronlc P 94- Pluronic F 108- Pluronic L 121 For tetronic structures see Table 2:

x=13, y=7 Tetronic 304 x=47, y=146. Tetronic 707. x=65,y=75 x=100, y=300 x=115, y= CaHnCgHtO H OH CsH17 o tO( 2 4O)1o CoHmCn (C2H4 )mo rsHa1O(CzH40)1o Ci7Ha5CO2CHzCHOHCH 17 33C 2laC3 1z 21 2 uHiaOa." C11H35CO2CBH12OI O z fl as zla aHu a (C11H35CO2)aCiH1uOz(OCzHOzoOH- C12H25N(C1H4 C12H25Nl(CzH4O)5H]z.- tsHa'INKCzHtlzsHlz Ethomeen 1860 CiiH2aCON(CzH4OH)z.- Gafamide CD 115--. C10.7Ha4.4CONKCaHtOhsHlz. Ethomid HT ClsH35N(CH3l (C2H4OH)2C1 Ethoquad O12 CllH23C02(C2H40)3H Pegosperse L.. C11Hz3COz(CzH4O)vH Hodag 40L -l- Ci1 aa 02( z 4O)nH Emerest 2660 C17Ha5CO2(C2H40)4uH Hodag -5 9929 999 9999999999 a aasa esseaaaesaemaassa 333%323558 +++l+l++++l+++l+l++l+i+++ ++++++++++++++++++++l++++l PPPPPQFPPPPNPPPP 1 Indicates that the film test was carried out with a film spreading solution containing 0.75 weight percent surfactant Q and 4.5 weight percent Butyl Carbitol".

desirable to have a slightly alkaline concentrate. One such film-forming alkaline concentrate embodying the teachings "1? P s! at ewe rrsper d ha the following formulation and a pH of 9.0

This concentrate, diluted with sixteen parts of fresh or sea water, when applied as an expanded foam to a 28 square feet aviation gasoline fire, produced the following results:

Diluent Fresh Water Sea Water Extinguishment Time (Sec.) 41 25% Bumback Time (Sec) 360 294 The foregoing results, when viewed against specifications for tire-fighting foam established by the US. fiat/Jae quite impressive, MlL-F-24385 requires an extinguishment time of less than 84 seconds and a 25 percent burnback time of greater than 240 seconds.

Another film-forming alkaline concentrate (pH of rine-containing surfactants is higher for those fluorinefree surfactants which are more soluble in hydrocarbon fuels; also, higher concentrations of fluorine-free surfactants are used where the aqueous diluent will contain higher concentrations of ionic materials. Either the fluoroaliphatic or the fluorine-free surfactant or both may consist of a mixture of two or more surface active m ate rials. a H A l g 7 H The following Table 7 shows representative formulations embodying the teachings of the present invention. The following base stock solution was used for each formulation:

Polyoxyethylene glycol, average MW 90,000

(Polyox N-10) CH,C0,H

9.0 parts 0.5 parts 30.0 parts 60.5 parts Test solutions were prepared by adding to the base stock the required amount of fluoroaliphatic surfactant and fluorine-free surfactant and diluting 6 ml of the resulting solution with 94 ml of either distilled water or sea water, as indicated. The sea water" is a synthetic salt mixture as defined by ASTM Test Method!) 1141-52 dissolved in distilled water to a concentration of 42 grams per liter.

The fluoroaliphatic surfactant for this table is a mixture of l 1.6 parts of C F CONl-IC J-I N"(CI l C l-l C'O and 1 part of C-, F cO H-N(CH C H NHC H CO H.

TABLE 7 Concentration, weight percent Agita- 50% Fluoro- Fluorinetion reburn aliphatic free sur- Speed Seal sistence back Diluent Fluorine-free surfactant surfactant factant (sec.) (sec.) (sec) (sec.)'-

Water 0. 36 1 15 +30 10 3 D0 Plin'onle P-94 0. 36 0. 25 3 +30 +15 2 Do Pluronic L-42 0. 36 0. 50 5 +30 +15 42 Do Pluronic L64 0. 36 0. 50 3 +30 +15 21 Do 0. 25 NC I +30 7 3 D0 Pluronci F-77- 0. 25 0. 1s 15 +30 5 13 D0 0. 25 0. 50 3 +30 +15 30 Do. 0. 18 NC +30 10 Do 0. 18 0. 50 12 +30 +15 30 D0 0. 18 0. 50 8 +30 +15 20 D0. 0. 12 NC 0 0 0 D0 0.12 0.50 NC 9 7 Do Pluronic 11-64.. 0. 12 0. NC +30 +15 0 Do. Pluronlc L-77 0.12 0. 25 NO +30 3 3 Do 0.36 12 +30 NR 9 ea Water 0.36 NC 0 NR 0 Water. Renex 31 0. 36 0. 25 2 +30 NR 36 Sea Water Rcncx 31 0.36 0. 25 1 +30 NR 3 Water CIZH25N( 011300211430 0. 36 0. 36 30 10 NR 9 Sea Water C zHz5N(CHa)2C2H4sO3 0. 36 0. 36 4 +30 NR 7 Water Pluronic P-94 0. 36 0. 25 2 30 NR 20 Sea water... 0.36 0.25 2 +30 NR 15 Water 0. 36 0. 25 3 +30 NR 4 Sea water do 0.36 0. 25 1 +30 NR 30 1 The violent agitation used in the Agitation Resistance test disrupts the film. When the Burnback Test immediately follows the Agitation Resistance Test the times are therefore relatively shorter than when the Agitation Test is not run (NR).

1 Pluronic is a Trademark of \Vyandotte Chemical 00., Wyandotte, Michigan. The composition of the indicated members of the series is believed to be as described in Table 8. following.

a The symbol NC indicates that the film from 5 drops of solution does not expand to completely cover the surface of the hydrocarbon under Test conditions. although 20 drops forms a complete seal.

4 ReneX-3l is a Trademark of Atlas Powder 00., Wilmington, Delaware, for a liquid polyoxyethylene ether alcohol nonionlc surfactant.

8.0) which met the requirements of the present invention had the following formulations:

C F SO NHCH CJ-LSO N'a 6.0 parts Butyl Carbitol 25.0 parts c u oso ua (Sipon WD) 5.0 parts Deionized Water 64.0 parts In general, the ratio of fluorine-free surfactant to fluorocarbon surfactant is not critical. Weight ratios of 1:25 to 10:1 are satisfactorily used, although the more usual weight ratio falls between 1:15 to 5:1. Generally speaking, the ratio of fluorine-free surfactants to fluooxide (Pluronics). Of this class, those with a polyethylene oxide content of 20 percent to 70 percent generally perform better than those with more or less polyethylene oxide. Those materials with a polypropylene oxide block of 1,750 to 3,250 molecular weight also show generally better performance-than those with higher or lower block of molecular weights. The following Table 8 lists some properties of his particular class of fluorine-free surfactants.

Table 8 Properties of Pluronic Surfactants Pluronics are HO(C H O)',,(C H' O)',,(C H,O) H block copolymers made by Wyandotte Chemical Corp.

Pluronic C,H,O (C,H,O), Emulsion Time No. M.W. Seconds L-3l 10 950 200+ L-35 50 950 200+ F-38 80 950 200+ L-42 1200 200+ L-44 40 1200 200+ L-6l 10 1750 I5 20 L-62 20 1750 20 1,-64 40 1750 5 F-68 80 1750 200+ L-72 20 2050 5 v P-75 50 2050 l5 F-77 70 2050 200+- L-Bl 10 2250 10 P-85 so 2250 15 F-88 80 2250 200+ L-92 20 2750 NR P-94 40 2750 10 F-98 80 2750 200+ L-l0l 10 3250 NR L-l03 3250 40 P-l05 50 3250 15 3O F-l08 so 3250 200+ L-l2l 10 4250 NR L-l2220 4250 NR F-l27 70 4250 NR In an effort to test the efficacy of a composition of the present invention on a large scale fire, a firefighting composition was formulated as follows:

Renex 31 0.5 parts Butyl carbitol 25.0 parts Acetic acid 1.5 parts Water 67.0 parts This concentrate, diluted with sixteen parts water, was found to have a film speed of 15 seconds and a seal time of 180 seconds when tested on the surface of heptane.

,The thus diluted aqueous solution was then comparatively tested on a 400 square feet (circular) white marine gasoline fire against the first composition shown in Table 7 which contained no fluorine-free surfactant.

FC FC-FF Surfactant Solution Surfactant Solution Time to Extinguishment 80 seconds seconds Bumback 10% 45 seconds 360 seconds 5 25% seconds 405 seconds 50% seconds 420 seconds The foregoing large scale fire test results show, quite vividly, the effect achieved by the combination of the fluoroaliphatic surfactant and the Renex 31 watersoluble synthetic irnputrescible organic fluorine-free surfactant. Thus, it will be observed that burnback times with the composition of the present invention are at least 3 to 6 times greater than the burnback times of the solution containing only a fluoroaliphatic surfactant. Burnback times are quite critical in fighting petroleum fed fires, particularly those involving aircraft, since rescue personnel are dispatched through the flame-extinguished areas at the earliest possible oppor tunity to effect personnel rescue. Obviously, the lives of the rescue personnel would be endangered if the fire-fighting composition did not afford a significant burnback time.

A primary limitation of previously known firefighting solutions involving fluorochemical surfactants and'water, such as those described in Tuve and Jablonski US Pat. No. 3,258,423, is that the fluorochemical component is used to provide both foaming and filmforming capability. This severely limits the choice of material which can be used. The present invention allows surfactant materials to be selected primarily on their ability for forming excellent vapor barrier films on fuel surfaces. If, in addition, foaming characteristics are desired, as forfire-fighting purposes, a foaming agent can be selected primarily on the basis of its foam producing and foam stability characteristics and used in conjunction with the film-forming agent. This foaming agent may be a fluorochemical surfactant, such as the perfluoroaliphatic carbonamido betaine suggested by Tuve and Jablonski or it may be a non-fluorinated foaming agent. One such common non-fluorinated foaming agent is the protein hydrolysate used to form the well known commercially available protein foam concentrates. Protein foam concentrates are wellknown materials for producing aqueous foams in firefighting. Their preparation, formulation and use is described in the article, Fire-fighting Foams by J. M. Perri, page 189 of FOAMS-THEORY AND INDUS- TRIAL APPLICATIONS, edited by J. J. Bikerman, Reinhold Publishing Corporation, New York, 1953. The concentrates are prepared by hydrolyzing any waste protein product such as soybean meal, hoofs, hair, feathers, or fish scales in either aqueous acid or aqueous base. Calcium hydroxide is a frequently used hydrolytic agent. Hydrolysis is normally carried out until a 2535 percent aqueous solution has a viscosity below 100 centistokes at 7 C. This concentrate is usually mixed with about 16 parts by volume of water arid pa rt s of gas, usually air, at the time of application to the fire.

Film forming solutions containing only a fluoroali- 5 phatic surfactant usually harm the efficiency of a protein foam system, the mixture resulting in a thin and unstable foam blanket. It has been found that film forming mixtures including a compatible fluorine-free surfactant do not significantly harm the effectiveness of a protein foam used therewith. For use in conjunction with protein foams, non-ionic fluorine-free surfactants are preferred in combination with a cationic fluorocarbon surfactant. In such uses, the protein foam-forming agent is normally used at 5 to 10 times by weight of the fluoroaliphatic surfactant and care must be taken to have the pH of the solution, either concentrate or final dispersion, within the range of 5 to 7 for optimum results.

The following Table 9 illustrates the flexibility which can be realized through the use of the teachings of the present invention in formulating foaming film forming compositions.

TABLE 9.--PROTEIN FOAM FORMULATIONS Film properties 50% Conc., Cone, Compati- Speed Seal back Fluorocarbon surfactant percent Fluorine-free surfactant percent bility (see) (see) (see) 818815 18 Nofilm +15 C'IFHCOZH'N(CH3):C3H5NHC2H4CO2H 0.36 Cloudy Very slow 0 0. 25 Heavy residue.

FIG. 1 is a graph which shows the relative evaporation rates of 25 grams of cyclohexane contained in a Petri dish measuring cm. in diameter by 2.7 cm. in height. Curves A-S and A-X show the evaporation rate of the cyclohexane under static conditions (A-S) and with agitation of the cyclohexane for four fours (A-X) when 0.6 grams ofa film-forming composition comprising 0.36 weight percent of C F,,,CONl-lC:,l-l l 1(Cl-l 0 and wa er wessl ssq n the YE QUQZ FHQ rf e Curves B-S (static) and B-X (agitation) show the evaporation rate of the cyclohexane with a vapor barrier film according to the invention placed thereover the film was formed with 0.6 gram of an aqueous composition comprising 0.36 weight percent of C7F15CONHC3H5N(CH3)2 0 and percent Pluronic P-94. Curves C-S (static) and C-X (agitation) show the loss by evaporation of the cyclohexane when 0.00216 gram of C1F CONCH H l:I

(Cl-19y 0 is United into the cyclohexane.

FIG. 2 is a graph which shows the rate of evaporation of a 25 grams sample of cyclohexane contained in a Petri dish measuring 5 cm. in diameter by 2.7 cm. in height. Curve A represents the evaporation loss of the cyclohexane with 0.6 gram of an aqueous solution of 0.25 weight percent Pluronic P-94 placed on the surface. Curve 1. r'fi'ssriisiiie evaporation rate otpirr' cyclohexane. Curves C (static) and C (agitation) show the evaporation rate of the cyclohexane with 0.6 gram of a 0.36 weight percent aqueous solution of C,F CONHC H N (C H I' placed on the surface of the cyclohexane. CurvesD (static) and D (agitation) show the evaporation rate of the cyclohexane when covered with a vapor barrier film formed with 0.6 gram of an aqueous film-forming composition comprising 0.36 weight percent C F CONHC H N (C H I and 0.25 weight percent Pluronic P94. Curve E represents the evaporation loss of the cyclohexane when 0.00216 gram of C F, CONHC H N (C H I" is mixed into the cyclohexane.

What is claimed is:

1. An aqueous concentrate composition useful for suppressing vaporization of liquid hydrocarbon comprising:

a. a film-forming component comprising a water soluble fluorinated surfactant of the formula rated monovalent organic radical having a terminal perfluoromethyl group containing from 3 to carbon atoms, in which the carbon atoms of the chain are subgroup, and Z is a water solubilizing polar group,

b. a synthetic imputrescible hydrocarbon-congruous organic fluorine-free surfactant water-soluble to at least about 0.02 percent by weight in water at 25 C. and which substantially completely emulsifies at least one phase of a mixture of equal volumes of cyclohexane and water at a concentration of about 0.1 to about 10 percent by weight of the water, in a ratio of 10:1 to 1:25 of fluorinated surfactant: fluorine-free surfactant,

c. a water-soluble stabilizer selected from the group consisting of alkyl ethers of alkylene glycol and glycerol,

(1. and up to weight percent water,

said concentrate composition upon dilution with water to contain not more than about 0.4 weight percent of said fluorinated surfactant being capable of forming a tough, durable, rapidly-forming and spreading film on the surface of the hydrocarbon thereby inhibiting the release of vapors therefrom.

2. A method of inhibiting the release of flammable vapors from liquid hydrocarbon materials comprising forming an aqueous solution of a. an aqueous concentrate composition comprising a water soluble fluorinated surfactant of the formula wherein (11,) where n is l or 2, is a fluorinated saturated monovalent organic radical having a terminal perfluoromethyl group and containing from 3 to 20 carbon atoms and at least 20 percent fluorine by weight, in which the carbon atoms of the chain are substituted only by fluorine, chlorine or hydrogen atoms with no more than one hydrogen or chlorine atom for every two carbon atoms, and in which a divalent oxygen or trivalent nitrogen atom, bonded only to carbon atoms, can be present in the skeletal chain, Q where m is an integer from 0 to 2, is a multivalent linking group, and Z is a water solubilizing polar group b. a synthetic imputrescible hydrocarbon-congruous organic fluorine-free surfactant water-soluble to at least about 0.02 percent by weight in water at 25 C. and which substantially completely emulsifies at least one phase of a mixture of equal volumes of cyclohexane and water at a concentration of about 0.1 to about 10 percent by weight of the water, in a ratio of 10:1 to 1:25 of fluorinated surfactant: fluorine-free surfactant, 0. a water-soluble stabilizer selected from the group consisting of alkyl ethers of alkylene glycol and glycerol,

d. and up to 95 percent water, with water to form an aqueous composition containing not more than about 0.4 weight percent of said fluorinated surfactant, applying said aqueous composition onto the surface of said liquid hydrocarbon and forming a tough, durable vapor barrier film on said surface thereby inhibiting the release of hydrocarbon vapors therefrom.

3. A composition useful for suppressing vaporization of liquid hydrocarbons comprising water, a watersoluble fluoroaliphatic surfactant and a synthetic imputrescible hydrocarbon-congruous organic fluorinefree surfactant water-soluble to at least about 0.02 percent by weight in water at 25 C., and which substantially completely emulsifies at least one phase of a mixture of equal volumes of cyclohexane and water at a concentration of about 0.1 to about 10 percent by weight of the water, said composition being substantially free from volatile flammable materials and being capable of forming a tough, durable, rapidly-forming and spreading film on the surface of the hydrocarbon thereby inhibiting the release of flammable vapors therefrom.

4. A composition according to claim 3 wherein said fluoroaliphatic surfactant contains a fluorinated aliphatic radical having a terminal perfluoromethyl group.

5. A composition according to claim 4 wherein the fluoroaliphatic surfactant has a surface tension of less than 23 dynes/cm. in aqueous solution at a concentration of about 0.25 percent by weight or less.

6. A composition according to claim 5 wherein the fluorine-free surfactant is a non-ionic surfactant.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent: No. 3,772,195 Dated November 13, 1973 Inventor) Vernon L. Francen It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Title page, under Related U.S. Application Data," after "Patent No 3,562,156" add which in turn is a continuationin-part of U.S. Application 722,630, filed April 19, 1968, now abandoned Column 1, line 3, after "Patent No 3,562,156" and before the period insert which in turn is a continuationin-part of U.S. Application 722, 630, filed April 19, 1968, now abandoned Column 1, line 7, after "Pat No 3,562,156", delete vaporization Signed and Sealed this Eighth Day Of November 1977 [SEAL] Arrest:

RUTH C. MASON LUTRELLE F. PARKER Arresting Officer Acting Commissioner of Patents and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,772,195 Dated November 13, 1973 lnventofls) Vernon L. Francen It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shownbelow:

Title page, under "Related U.S. Application Data," after "Patent No 3,562,156" add which in turn is a continuationin-part of U.S. Application 722,630, filed April 19, 1968, now abandoned Column 1, line 3, after "Patent No. 3,562,156" and before the period insert which in turn is a continuationin-part of U.S. Application 722,630, filed April 19, 1968, now abandoned Column 1, line 7, after "Pat No. 3,562,156", delete vaporization 7 Signed and Scaled this Eighth Day Of November 1977 [SEAL] Attest:

RUTH C. MASON LUTRELLE F. PARKER Arresting Officer Acting Commissioner of Patents and Trademarks 

2. A method of inhibiting the release of flammable vapors from liquid hydrocarbon materials comprising forming an aqueous solution of a. an aqueous concentrate composition comprising a water soluble fluorinated surfactant of the formula (Rf)nQmZ wherein (Rf)n, where n is 1 or 2, is a fluorinated saturated monovalent organic radical having a terminal perfluoRomethyl group and containing from 3 to 20 carbon atoms and at least 20 percent fluorine by weight, in which the carbon atoms of the chain are substituted only by fluorine, chlorine or hydrogen atoms with no more than one hydrogen or chlorine atom for every two carbon atoms, and in which a divalent oxygen or trivalent nitrogen atom, bonded only to carbon atoms, can be present in the skeletal chain, Qmwhere m is an integer from 0 to 2, is a multivalent linking group, and Z is a water solubilizing polar group b. a synthetic imputrescible hydrocarbon-congruous organic fluorine-free surfactant water-soluble to at least about 0.02 percent by weight in water at 25* C. and which substantially completely emulsifies at least one phase of a mixture of equal volumes of cyclohexane and water at a concentration of about 0.1 to about 10 percent by weight of the water, in a ratio of 10:1 to 1:25 of fluorinated surfactant: fluorine-free surfactant, c. a water-soluble stabilizer selected from the group consisting of alkyl ethers of alkylene glycol and glycerol, d. and up to 95 percent water, with water to form an aqueous composition containing not more than about 0.4 weight percent of said fluorinated surfactant, applying said aqueous composition onto the surface of said liquid hydrocarbon and forming a tough, durable vapor barrier film on said surface thereby inhibiting the release of hydrocarbon vapors therefrom.
 3. A composition useful for suppressing vaporization of liquid hydrocarbons comprising water, a water-soluble fluoroaliphatic surfactant and a synthetic imputrescible hydrocarbon-congruous organic fluorine-free surfactant water-soluble to at least about 0.02 percent by weight in water at 25* C., and which substantially completely emulsifies at least one phase of a mixture of equal volumes of cyclohexane and water at a concentration of about 0.1 to about 10 percent by weight of the water, said composition being substantially free from volatile flammable materials and being capable of forming a tough, durable, rapidly-forming and spreading film on the surface of the hydrocarbon thereby inhibiting the release of flammable vapors therefrom.
 4. A composition according to claim 3 wherein said fluoroaliphatic surfactant contains a fluorinated aliphatic radical having a terminal perfluoromethyl group.
 5. A composition according to claim 4 wherein the fluoroaliphatic surfactant has a surface tension of less than 23 dynes/cm. in aqueous solution at a concentration of about 0.25 percent by weight or less.
 6. A composition according to claim 5 wherein the fluorine-free surfactant is a non-ionic surfactant. 